Paint or plaster?

chabsey

I am in the middle of doing up a house and have a problem with the kitchen-to-be. Basically at the moment a few of the walls are in a pretty bad state, old paint, sections uneven and marks/glue from tiles that were there.

I had thought of using a plasterer to skim the whole thing and then paint it but our electrician was looking at it yesterday and suggested hiring a sander and stripping the walls right back. He said that all the paint/gunk on the walls could be sanded right back and the wall then painted.

Thing is, if we sanded right back we'd be at the dusty white plaster level and obviously can't paint on top of that. So, assuming I sand right back is there something I can coat the raw plaster with to give a smooth, paint-ready surface? Or should I just forget sanding altogether?

Idleater

Did the same in my house.

When I took off the paint (*see later) and was down to the bare dusty plaster I first washed it down with water and sugarsoap. Very quick, just to get rid of most of the dust. Then I made up a mix of PVA (wood glue) and water. I don't know the ratio but there was perhaps 1 litre of water and a small dallop of glue. Mix this about and you get a milky concoction. I "painted" this onto the wall and let it dry.
The next step was to put on the first coat of paint which was normal emulsion with a small bit of water added to it. I rollered this onto the walls.
Finally when this was dry, I painted 2 coats of kitchen and bathroom paint onto the walls.

It may have been overkill perhaps but the effect of all the pre coatings is that the plaster that was on the wall is sealed and the final coats of actual paint grip onto something other then pure plaster.

I learned this from the previous owner of the house!
They had painted straight onto the plaster and what basically happened was that as the paint dried, the moisture was drawn into the plaster. I was able to literally peel off the entire coats of paint off the wall!

Bit of work but worth it all the same.

L.

Alun

You can get emulsions that are specifically made for painting straight onto plastered walls. I've used this as an "undercoat" for whatever other finish I was applying, be it normal silk emulsion or bathroom / kitchen type paint with no problems.

chabsey

nereid wrote:

It may have been overkill perhaps but the effect of all the pre coatings is that the plaster that was on the wall is sealed and the final coats of actual paint grip onto something other then pure plaster.

Bit of work but worth it all the same.

L.

Sounds like what I want to do, but I'm not sure the plaster will be the same as you dealt with. It's not plaster board, it's an old house and the plaster is actually on top of the concrete walls. So when I get down to the plaster level it'll be that really crumbly white stuff. Do you think your method would work on this type of wall? I know it's hard to tell without seeing, but your experience will help with my decision I think.

Idleater

chabsey wrote:

Sounds like what I want to do, but I'm not sure the plaster will be the same as you dealt with. It's not plaster board, it's an old house and the plaster is actually on top of the concrete walls. So when I get down to the plaster level it'll be that really crumbly white stuff. Do you think your method would work on this type of wall? I know it's hard to tell without seeing, but your experience will help with my decision I think.

Right, that is interesting.

How old (just wondering) is the house?

The kitchen that I explained earlier in my previous post was "modern" (probably 1990 or so) skimcoat plaster on plasterboard as the kitchen is an extension. (More like "extension" but that is another matter ).

However, I also have some 1880's plaster (nice white lime and horsehair) walls in the other rooms of the house.

Unfortunately for me, the condition of the wall surface was not the best when I got down to it, so I ended up skimcoating them all and thus patching the holes and leaving me a nice new surface to paint.

I would recommend in your case that if the overall surface is smooth when you sand it down you would get away with doing the sealing with glue/paint as I described before.

You could try it on a small bit of wall to see what happens. In any case, I would not skim over the mucky glue surface that you say is there at the moment.

L.

rooferPete

Hi,

Take care when applying skimcoat over a lime based plaster, skimcoat can seal the walls whereas lime based plaster worked with the wall allowing it to breathe.

The side effect can be walls that appear damp and actually draw the moisture into the building because building with lime is an art unto itself.

Worst case, dry line the walls using laths that allow air to circulate behind the new boards.

.

Idleater

rooferPete wrote:

Hi,

Take care when applying skimcoat over a lime based plaster, skimcoat can seal the walls whereas lime based plaster worked with the wall allowing it to breathe.

The side effect can be walls that appear damp and actually draw the moisture into the building because building with lime is an art unto itself.

Worst case, dry line the walls using laths that allow air to circulate behind the new boards.

.

Interesting stuff.

As it happens, that is what I actually did in my case. I put up 2x1 batons and insulation on the external walls and put back up plasterboard onto these. I did this for insulation purposes as the room was quite "cool" during the autumn/winter/spring.

However, on the internal wall, I just plastered directly over the existing plaster. This is not a structurall wall - just a ye olde partition. Im sure that it wont matter too much in this case that I have plastered directly over the lime plaster. It will be undergoing redevelopment in the next couple of years anyway.

So far I have not noticed any damp or coldness on any of the walls that I have done up. What sort of timeframe would the problems that you refer to arise in?

Just wondering then, in relation to the Original Poster's situation, what would be the best way of patching his plaster (if needs be)? Is what I suggested okay or is there some better way?

L.